Today, more than ever, audiences are surrounded by imaginary worlds in which a wide variety of products and activities can be fully explored through multiple media windows. Imaginary worlds allow members of the audience to enter vicariously in the narrative space, spending a certain amount of time in speculative and explorative activities, experiencing the ‘possible world’ through the stories set within it. According to this, it is possible to differentiate between story and storyworld. While ‘stories’ are self-enclosed arrangements of causal events that come to an end in a certain period of time, ‘storyworlds’ are mental constructions shared between recipients and authors in which new storylines can be developed. This paper aims to discuss the implication of world-building activity for the design practice. Considering narratives and world-making practices as a matter of design, this essay will tackle the following question: how can a designer use the creation of storyworlds in his practice to activate new perspectives on specific contexts? In doing so, the first part of the essay is a brief summary of how imaginary worlds have evolved through the decades. Then, the second part is devoted to the presentation of the so-called Storyworld Canvas, one of the narrative design tools developed in our research group in order to support both storytelling practice and storyworld creation. Finally, the paper describes the project Watchmen of the Nine with the aim of analysing its storyworld from the perspective of the design domain, considering storytelling and world-building activities as ways to enrich the design practice.